GDB Eigen Debugging with Conditional Breakpoints Failing

Question

I'm trying to debug with GDB using conditional breakpoints on an Eigen object. For instance, I'd like to break when any values in my vector are nonzero. I would do this in GDB:

break cpp/File.cpp:143 if (v != 0).any()

However, this doesn't work. GDB gives this:

Could not find operator!=

even though this is perfectly valid syntax. Moreover, a conditional breakpoint like

break cpp/File.cpp:143 if v[0] != 0

gives this error in GDB:

Error in testing breakpoint condition:
Couldn't get registers: No such process.
An error occurred while in a function called from GDB.
Evaluation of the expression containing the function
(Eigen::DenseCoeffsBase<Eigen::Array<int, 3, 1, 0, 3, 1>, 1>::operator[](long)) will be abandoned.
When the function is done executing, GDB will silently stop.

The code was compiled with -O0 -g -fno-inline . How do I debug the contents of an Eigen object?

Answer 1

According to this question , (sometimes) GDB seems to have problems with overloaded operators. You could try one of these alternatives:

if (! v.isZero())

if (! v.cwiseEqual(0).all()) 

And instead of if v[0] != 0 you could try one of these:

 if (v.data()[0] != 0)

 if (v.coeff(0) != 0)